
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User:龙宝
 * Date:2022-11-24
 * Time:20:35
 */
public class UserDao {
    //1、根据用户名来查询用户的详情——隐含约束，用户名唯一
    public User selectByName(String username) {
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        try {
            //1、和数据库建立连接
            connection = DBUtil.getConnection();

            //2、构造sql
            String sql = "select * from user where username = ?";
            statement = connection.prepareStatement(sql);
            statement.setString(1,username);

            //3、执行sql
            resultSet  = statement.executeQuery();

            //4、遍历结果集合
            if(resultSet.next()) {
                User user = new User();
                user.setUserId(resultSet.getInt("userId"));
                user.getUsername(resultSet.getString("username"));
                user.setPassword(resultSet.getString("password"));
                return user;
            }

        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            DBUtil.close(connection,statement,resultSet);
        }
        return  null;
    }

    //根据用户id来查询用户详情——在获取用户信息的时候，
    public User selectById(int userId) {
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;

        try {
            connection = DBUtil.getConnection();
            String sql = "select * from user where userId = ?";
            statement = connection.prepareStatement(sql);
            statement.setInt(1,userId);

            resultSet = statement.executeQuery();

            if(resultSet.next()) {
                User user = new User();
                user.setUserId(resultSet.getInt("userId"));
                user.setUsername(resultSet.getString("username"));
                user.setPassword(resultSet.getString("password"));
                return user;
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            DBUtil.close(connection,statement,resultSet);
        }
        return null;
    }
}
